A fuel gasification system has been developed to produce gasification gas, using coal, biomass, waste plastic, various wet wastes or the like as fuel.
In the fuel gasification system, tar is contained in gasification gas produced in a gasification furnace. Especially heavy oil component of the tar is highly viscous and tends to attach to piping or the like, resulting disadvantageously in clogging of the piping or the like in a long-term operation.
In order to overcome such disadvantage, there has been, for example, a fuel gasification system as shown in FIG. 1 which comprises a gasification furnace 100 for partly oxidizing fuel such as coal, biomass, waste plastic or various wet wastes into gasification gas, a steam generator 101 for generating steam to be fed to the furnace 100, a scrubber 102 for separating tar and the like from the gasification gas produced in the furnace 100, an electric dust collector 103 for capturing particles and the like from the gasification gas having been free from the tar and the like in the scrubber 102, an internal-combustion engine 104 such as gas engine or gas turbine driven by burning as fuel the gasification gas having been free from the particles and the like in the collector 103, an electric generator 105 driven by the engine 104, a thermal energy recovery device 106 comprising, for example, a heat exchanger for heat recovery of the gas discharged from the engine 104, a flue 107 for discharging to atmosphere the exhaust gas having been heat-recovered in the recovery device 106, a tar/water separator 108 for separating tar and water having been separated from the gasification gas in the scrubber 102, a tar tank 109 for recovering the tar having been separated in the separator 108 and a combustion furnace 110 for burning the tar recovered in the tank 109.
In the fuel gasification system shown in FIG. 1, the fuel such as coal, biomass, waste plastic or various wet wastes is partly oxidized in the gasification furnace 100 into gasification gas which is introduced into the scrubber 102 where water is sprayed to the gasification gas to separate tar and the like and condense steam in the gasification gas. The gasification gas having been free from the tar and the like is introduced into the electric dust collector 103 where particles and the like in the gasification gas are captured. The gasification gas having been free from the particles and the like is burned as fuel to drive the engine 104 to generate electricity in the electric generator 105. The exhaust gas from the engine 104 is heat-exchanged with air in the thermal energy recovery device 106 for heat recovery and is discharged to atmosphere through the flue 107.
The tar having been separated from the gasification gas by spraying water in the scrubber 102 is separated from the water in the tar/water separator 108. The tar having been separated from the water in the separator 108 is recovered in the tar tank 109 and is burned in the combustion furnace 110. The water having been separated from the tar in the tar/water separator 108 is turned into steam in the steam generator 101 and is fed to the gasification furnace 100 together with the air heated in the thermal energy recovery device 106.
In the conventional fuel gasification system, the gasification furnace 100 may be followed by a reforming furnace to which oxygen is fed to partly burn the gasification gas for decomposition of the tar.
State of the art technology of a fuel gasification system for partly oxidizing fuel such as coal through an oxidizing agent into gasification gas is shown, for example, in Reference 1.    [Reference 1] JP 2000-355693A